Modern computer controlled label printers make it possible to print a highly individualized label for each of a series of product units. Such things as contents identification, product weight, and quality control data can be ascertained and a detailed label printed for each package. The term package as used herein is understood to include cartons, containers, bales, etc. for products. The problem presently preventing the most efficient use of these printers is the fact that there has not been found an acceptable means of transferring the label from the printer to the package. At present, the printed labels are handled either manually or mechanically to apply adhesive to the printed label and apply it to the package. The handling of adhesive in this operation is awkward and messy. Precut pressure-sensitive labels carried on a release coated backing material present one alternative to the application of adhesive during the labeling process; however, no mechanism has been found which is capable of coacting with printers of the type described to peel the printed label away from the backing material and position it properly on the applicator.
Pressure-sensitive labels are commonly provided on a backing material which is somewhat more flexible than the label itself. This allows the label to be separated from the backing simply be bending the backing sharply away from the label, which is usually done by drawing the backing over a fairly sharp stripping bar or plate. The less flexible label then separates from the backing and remains relatively straight. To reliably separate the label from the backing using this method requires a great deal of force, however, because the backing must be pulled tightly over a sharp edge to get the required sharp bend. This causes high frictional forces between the backing and the stripping bar which increases with the width of the label and backing strip. The drive mechanism provided in the printers is usually not sufficiently powerful to provide the force required to pull the labels over a stripper bar. In addition, typical drive systems in these printers utilize pins which engage perforations in the backing material so that even if the drive system were powerful enough, the increased force on the pins would tend to tear the backing material.
A solution to this problem is the utilization of an auxiliary drive downstream of the printer to provide enough tension on the backing material to pull it tightly over the stripping bar. However, coordination of the two drive systems so that the label is stripped as it emerges from the printer requires complicated controls since the printer drive advances the label incrementally rather than continuously.
An additional problem is encountered in the handling of pressure-sensitive labels, whether being advanced out of a printer or from a roll of pre-printed labels. This results from the fact that the backing material must be stripped away from the label in order to expose the adhesive side of the label prior to its application to the package and yet the only means of controlling the label is to control the backing to which it is attached. It is common to provide an applicator which includes a vacuum platen to acquire the label from the backing material and hold it with the adhesive surface exposed, so that the vacuum platen can then be moved to contact the package with the adhesive surface of the label. A problem arises, however, in attempting to transfer the label from the backing material to the vacuum platen since the stripping bar is generally stationary and thus the label is propelled forward as the backing is stripped away. This means that either the vacuum platen must be moved with the label or the label must be fully liberated from the backing before being acquired by the vacuum platen.
Neither of these approaches is completely satisfactory. Attempting to coordinate the movement of the vacuum platen with the advance of the label can require complicated controls, and entirely liberating the label before acquiring it results in a lack of positive control of the label so that the label, especially if it is relatively large, may become folded or wrinkled before being acquired by the vacuum platen.